U.S. patent application number 17/094155 was filed with the patent office on 2021-02-25 for devices, systems, and methods for assessing a vessel.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Fergus MERRITT, Jinhyoung PARK.
Application Number | 20210052174 17/094155 |
Document ID | / |
Family ID | 1000005210238 |
Filed Date | 2021-02-25 |
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United States Patent
Application |
20210052174 |
Kind Code |
A1 |
PARK; Jinhyoung ; et
al. |
February 25, 2021 |
DEVICES, SYSTEMS, AND METHODS FOR ASSESSING A VESSEL
Abstract
An intravascular system includes at least one pressure-sensing
instrument sized and shaped for introduction into a vessel of a
patient; a processing unit in communication with the
pressure-sensing instrument, the processing unit configured to:
obtain proximal pressure measurements for at least one cardiac
cycle of the patient while the pressure-sensing instrument is
positioned proximal of a stenosis of the vessel; obtain distal
pressure measurements while the pressure-sensing instrument is
positioned distal of the stenosis; select a diagnostic window
within a cardiac cycle by identifying a change in sign of a slope
associated with the proximal and/or distal pressure measurements,
wherein the diagnostic window encompasses only a portion of the
cardiac cycle of the patient; calculate a pressure ratio between
the distal and proximal obtained during the diagnostic window; and
output the calculated pressure ratio to a display device in
communication with the processing unit.
Inventors: |
PARK; Jinhyoung; (RANCHO
CORDOVA, CA) ; MERRITT; Fergus; (RANCHO CORDOVA,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
EINDHOVEN |
|
NL |
|
|
Family ID: |
1000005210238 |
Appl. No.: |
17/094155 |
Filed: |
November 10, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15745651 |
Jan 17, 2018 |
10849512 |
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PCT/EP2016/066917 |
Jul 15, 2016 |
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17094155 |
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62194066 |
Jul 17, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/02158 20130101;
A61B 5/7239 20130101; A61B 5/6852 20130101; A61B 5/6851 20130101;
A61B 5/352 20210101; A61B 5/02007 20130101 |
International
Class: |
A61B 5/0215 20060101
A61B005/0215; A61B 5/00 20060101 A61B005/00; A61B 5/02 20060101
A61B005/02 |
Claims
1. A system comprising: a processor configured for communication
with an intravascular pressure-sensing instrument and configured
to: obtain pressure measurements for a cardiac cycle of a patient
from the intravascular pressure-sensing instrument while the
intravascular pressure-sensing instrument is positioned within a
vessel; calculate, for the cardiac cycle, a plurality of slopes of
the pressure measurements; determine a first change in sign of the
plurality of slopes from a first sign to a second sign; determine a
second change in sign of the plurality of slopes from the second
sign to the first sign; select a diagnostic window within the
cardiac cycle based on the first change in sign and the second
change in sign; calculate a pressure ratio based on a subset of the
pressure measurements obtained during the diagnostic window; and
output the calculated pressure ratio to a display device in
communication with the processor.
2. The system of claim 1, wherein the processor is configured to:
determine a starting point of the diagnostic window based on the
first change in sign; and determine an ending point of the
diagnostic window based on the second change in sign.
3. The system of claim 2, wherein the processor is configured to:
determine a peak pressure measurement of the pressure measurements
based on the first change in sign; determine a maximum negative
slope of the plurality of slopes occurring after the peak pressure
measurement; and determine the starting point of the diagnostic
window based on the maximum negative slope.
4. The system of claim 3, wherein processor is configured to:
calculate each of the plurality of slopes over a same segment
duration; determine the peak pressure measurement based on a first
multiplier and the segment duration.
5. The system of claim 4, wherein the processor is configured to
determine the starting point of the diagnostic window such that the
starting point is offset from the maximum negative slope by a first
period.
6. The system of claim 5, wherein the processor is configured to:
determine a minimum pressure measurement within the cardiac cycle
based on the second change in sign; and determine the ending point
of the diagnostic window such that the ending point is offset from
the minimum pressure measurement by a second period.
7. The system of claim 6, wherein a duration of the first period is
different from a duration of the second period.
8. The system of claim 6, wherein the processor is configured to:
determine the minimum pressure measurement based on a second
multiplier and the segment duration, wherein the second multiplier
is different from the first multiplier.
9. The system of claim 8, wherein the processor is configured to
shift the plurality of slopes in time based on a third multiplier
and the segment duration.
10. The system of claim 1, wherein the processor is further
configured to: calculate each of the plurality of slopes over a
first segment duration; and calculate a further plurality of slopes
in a further cardiac cycle, wherein the processor is configured to
calculate each of the further plurality of slopes over a second
segment duration different from the first segment duration.
11. The system of claim 10, wherein the processor is configured to
determine the second segment duration based on a duration of the
cardiac cycle.
12. The system of claim 1, wherein the processor is configured to
calculate the plurality of slopes for a plurality of corresponding
time periods, wherein consecutive time periods at least partially
overlap in time.
13. The system of claim 1, wherein the processor is further
configured to determine, based on at least one of the first change
in sign or the second change in sign, at least one of a minimum
pressure measurement, a peak pressure measurement, a beginning of
the cardiac cycle, an ending of the cardiac cycle, a beginning of
systole, an ending of diastole, a starting point of the diagnostic
window, or an ending point of the diagnostic window.
14. The system of claim 1, further comprising the intravascular
pressure-sensing instrument.
15. The system of claim 14, wherein the intravascular
pressure-sensing instrument comprises at least one of a catheter or
a guide wire.
16. The system of claim 1, wherein the diagnostic window
encompasses only a portion of the cardiac cycle of the patient.
Description
CROSS-REFERENCE TO PRIOR APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/745,651, filed on Jan. 17, 2018, which is
the U.S. National Phase application under 35 U.S.C. .sctn. 371 of
International Application No. PCT/EP2016/066917, filed on Jul. 15,
2016, which claims the benefit of U.S. Provisional Patent
Application No. 62/194,066, filed on Jul. 17, 2015. These
applications are hereby incorporated by reference herein.
TECHNICAL FIELD
[0002] The present disclosure relates generally to the assessment
of vessels and, in particular, the assessment of the severity of a
blockage or other restriction to the flow of fluid through a
vessel. Aspects of the present disclosure are particularly suited
for evaluation of biological vessels in some instances. For
example, some particular embodiments of the present disclosure are
specifically configured for the evaluation of a stenosis of a human
blood vessel.
BACKGROUND
[0003] A currently accepted technique for assessing the severity of
a stenosis in a blood vessel, including ischemia causing lesions,
is fractional flow reserve (FFR). FFR is a calculation of the ratio
of a distal pressure measurement (taken on the distal side of the
stenosis) relative to a proximal pressure measurement (taken on the
proximal side of the stenosis). FFR provides an index of stenosis
severity that allows determination as to whether the blockage
limits blood flow within the vessel to an extent that treatment is
required. The normal value of FFR in a healthy vessel is 1.00,
while values less than about 0.80 are generally deemed significant
and require treatment. Common treatment options include angioplasty
and stenting.
[0004] Coronary blood flow is unique in that it is affected not
only by fluctuations in the pressure arising proximally (as in the
aorta) but is also simultaneously affected by fluctuations arising
distally in the microcirculation. Accordingly, it is not possible
to accurately assess the severity of a coronary stenosis by simply
measuring the fall in mean or peak pressure across the stenosis
because the distal coronary pressure is not purely a residual of
the pressure transmitted from the aortic end of the vessel. As a
result, for an effective calculation of FFR within the coronary
arteries, it is necessary to reduce the vascular resistance within
the vessel. Currently, pharmacological hyperemic agents, such as
adenosine, are administered to reduce and stabilize the resistance
within the coronary arteries. These potent vasodilator agents
reduce the dramatic fluctuation in resistance (predominantly by
reducing the microcirculation resistance associated with the
systolic portion of the heart cycle) to obtain a relatively stable
and minimal resistance value.
[0005] However, the administration of hyperemic agents is not
always possible or advisable. First, the clinical effort of
administering hyperemic agents can be significant. In some
countries (particularly the United States), hyperemic agents such
as adenosine are expensive, and time consuming to obtain when
delivered intravenously (IV). In that regard, IV-delivered
adenosine is generally mixed on a case-by-case basis in the
hospital pharmacy. It can take a significant amount of time and
effort to get the adenosine prepared and delivered to the operating
area. These logistic hurdles can impact a physician's decision to
use FFR. Second, some patients have contraindications to the use of
hyperemic agents such as asthma, severe COPD, hypotension,
bradycardia, low cardiac ejection fraction, recent myocardial
infarction, and/or other factors that prevent the administration of
hyperemic agents. Third, many patients find the administration of
hyperemic agents to be uncomfortable, which is only compounded by
the fact that the hyperemic agent may need to be applied multiple
times during the course of a procedure to obtain FFR measurements.
Fourth, the administration of a hyperemic agent may also require
central venous access (e.g., a central venous sheath) that might
otherwise be avoided. Finally, not all patients respond as expected
to hyperemic agents and, in some instances, it is difficult to
identify these patients before administration of the hyperemic
agent.
[0006] Accordingly, there remains a need for improved devices,
systems, and methods for assessing the severity of a blockage in a
vessel and, in particular, a stenosis in a blood vessel. In that
regard, there remains a need for improved devices, systems, and
methods for assessing the severity of a stenosis in the coronary
arteries that do not require the administration of hyperemic
agents.
SUMMARY
[0007] Embodiments of the present disclosure are configured to
assess the severity of a blockage in a vessel and, in particular, a
stenosis in a blood vessel. In some particular embodiments, the
devices, systems, and methods of the present disclosure are
configured to assess the severity of a stenosis in the coronary
arteries without the administration of a hyperemic agent. A subset
of intravascular pressure measurements obtained during a diagnostic
window can be used to calculate a pressure ratio. The diagnostic
window can be determined without utilizing electrocardiogram (ECG)
data, in some instances. Rather, in such instances, the
intravascular pressure measurements can be divided into different
time periods, and slopes respectively associated with each time
period can be used to identify one or more features of the
intravascular pressure measurements, a cardiac cycle of the
patient, and/or the diagnostic window.
[0008] In some instances, an intravascular system is provided. The
system includes at least one pressure-sensing instrument sized and
shaped for introduction into a vessel of a patient; a processing
unit in communication with the at least one pressure-sensing
instrument, the processing unit configured to: obtain proximal
pressure measurements for at least one cardiac cycle of the patient
from the at least one pressure-sensing instrument while the at
least one pressure-sensing instrument is positioned within the
vessel at a position proximal of a stenosis of the vessel; obtain
distal pressure measurements for the at least one cardiac cycle of
the patient from the at least one pressure-sensing instrument while
the at least one pressure-sensing instrument is positioned within
the vessel at a position distal of the stenosis of the vessel;
select a diagnostic window within a cardiac cycle of the patient by
identifying a change in sign of a slope associated with at least
one of the proximal pressure measurements or the distal pressure
measurements, wherein the diagnostic window encompasses only a
portion of the cardiac cycle of the patient; calculate a pressure
ratio between the distal pressure measurements obtained during the
diagnostic window and the proximal pressure measurements obtained
during the diagnostic window; and output the calculated pressure
ratio to a display device in communication with the processing
unit.
[0009] In some embodiments, the processing unit is configured to
select a diagnostic window without using electrocardiogram (ECG)
data. In some embodiments, the proximal and distal pressure
measurements are obtained without administration of a hyperemic
agent. In some embodiments, the processing circuit is further
configured to calculate the slope over multiple time periods within
the cardiac cycle. In some embodiments, a single time period
encompasses only a portion of the cardiac cycle. In some
embodiments, time periods within the cardiac cycle have the same
duration. In some embodiments, the processing circuit is further
configured to calculate the slope over multiple time periods of a
further cardiac cycle, wherein the time periods of the further
cardiac cycle have a different duration than the time periods of
the cardiac cycle. In some embodiments, a duration of the time
periods is based on a duration of a cardiac cycle. In some
embodiments, a duration of the time periods is based on a duration
of time periods in one or more previous cardiac cycles. In some
embodiments, consecutive time periods at least partially overlap in
time. In some embodiments, a starting point of consecutive time
periods are offset based on an acquisition rate of the at least one
pressure-sensing instrument.
[0010] In some embodiments, the processing unit is further
configured to identify a sign change of the slope based on
calculation of the slope over the plurality of time periods. In
some embodiments, the processing unit is further configured to
determine, based on the sign change of the slope, at least one of:
a minimum pressure measurement, a peak pressure measurement, a
beginning of the cardiac cycle, an ending of the cardiac cycle, a
beginning of systole, an ending of diastole, a starting point of
the diagnostic window, or an ending point of the diagnostic window.
In some embodiments, the processing unit is further configured to
determine a starting point of the diagnostic window based on the
sign change of the slope. In some embodiments, the starting point
of the diagnostic window is offset from the sign change of the
slope. In some embodiments, the processing unit is further
configured to determine a peak pressure measurement based on the
sign change of the slope. In some embodiments, the peak pressure
measurement is offset from the sign change of the slope. In some
embodiments, the processing unit is further configured to determine
a starting point of the diagnostic window based on the peak
pressure measurement. In some embodiments, the starting point of
the diagnostic window is offset from the peak pressure measurement.
In some embodiments, the processing unit is further configured to
determine a maximum negative slope occurring after the peak
pressure measurement. In some embodiments, the processing unit is
further configured to determine a starting point of the diagnostic
window based on the maximum negative slope. In some embodiments,
the starting point of the diagnostic window is offset from the
maximum negative slope. In some embodiments, the processing unit is
further configured to determine a further sign change of the slope.
In some embodiments, the processing unit is further configured to
determine a minimum pressure measurement based on the further sign
change of the slope. In some embodiments, the minimum pressure
measurement is offset from the further sign change of the slope. In
some embodiments, the processing unit is further configured to
determine an ending point of the diagnostic window based on the
minimum pressure measurement. In some embodiments, the ending point
of the diagnostic window is offset from the minimum pressure
measurement.
[0011] In some embodiments, the at least one pressure-sensing
instrument comprises: a first pressure-sensing instrument sized and
shaped to obtain the proximal pressure measurements while
positioned within the vessel at a position proximal of the stenosis
of the vessel; and a second pressure-sensing instrument sized and
shaped to obtain the distal pressure measurements while positioned
within the vessel at a position distal of the stenosis of the
vessel. In some embodiments, at least one of the first or second
pressure-sensing instruments comprises a catheter, a guide wire, or
a guide catheter. In some embodiments, the first pressure-sensing
instrument is a catheter and the second pressure-sensing instrument
is a guide wire.
[0012] In some instances, a method of evaluating a vessel of a
patient is provided. The method includes receiving, at a processing
unit in communication with at least one pressure-sensing instrument
sized and shaped for introduction into a vessel of the patient,
proximal pressure measurements for at least one cardiac cycle of
the patient while the at least one pressure-sensing instrument is
positioned within the vessel at a position proximal of a stenosis
of the vessel; receiving, at the processing unit, distal pressure
measurements for the at least one cardiac cycle of the patient
while the at least one pressure-sensing instrument is positioned
within the vessel at a position distal of the stenosis of the
vessel; selecting, using the processing unit, a diagnostic window
within a cardiac cycle of the patient by identifying a change in
sign of a slope associated with at least one of the proximal
pressure measurements or the distal pressure measurements, wherein
the diagnostic window encompasses only a portion of the cardiac
cycle of the patient; calculating, using the processing unit, a
pressure ratio between the distal pressure measurements obtained
during the diagnostic window and the proximal pressure measurements
obtained during the diagnostic window; and outputting, using the
processing unit, the calculated pressure ratio to a display device
in communication with the processing unit.
[0013] In some embodiments, the selecting a diagnostic window does
not include using electrocardiogram (ECG) data. In some
embodiments, the obtaining proximal pressure measurements and the
obtaining distal pressure measurements do not include administering
a hyperemic agent. In some embodiments, the method further includes
calculating, using the processing circuit, the slope over multiple
time periods within the cardiac cycle. In some embodiments, a
single time period encompasses only a portion of the cardiac cycle.
In some embodiments, time periods within the cardiac cycle have the
same duration. In some embodiments, the method further includes
calculating the slope over multiple time periods of a further
cardiac cycle, wherein the time periods of the further cardiac
cycle have a different duration than the time periods of the
cardiac cycle. In some embodiments, a duration of the time periods
is based on a duration of a cardiac cycle. In some embodiments, a
duration of the time periods is based on a duration of time periods
in one or more previous cardiac cycles. In some embodiments,
consecutive time periods at least partially overlap in time. In
some embodiments, a starting point of consecutive time periods are
offset based on an acquisition rate of the at least one
pressure-sensing instrument.
[0014] In some embodiments, the method further includes
identifying, using the processing unit, a sign change of the slope
based on the slope calculated over the plurality of time periods.
In some embodiments, the method further includes determining, using
the processing unit and based on the sign change of the slope, at
least one of: a minimum pressure measurement, a peak pressure
measurement, a beginning of the cardiac cycle, an ending of the
cardiac cycle, a beginning of systole, an ending of diastole, a
starting point of the diagnostic window, or an ending point of the
diagnostic window. In some embodiments, the method further includes
determining, using the processing unit, a starting point of the
diagnostic window based on the sign change of the slope. In some
embodiments, the starting point of the diagnostic window is offset
from the sign change of the slope. In some embodiments, the method
further includes determining, using the processing unit, a peak
pressure measurement based on the sign change of the slope. In some
embodiments, the peak pressure measurement is offset from the sign
change of the slope. In some embodiments, the method further
includes determining, using the processing unit, a starting point
of the diagnostic window based on the peak pressure measurement. In
some embodiments, the starting point of the diagnostic window is
offset from the peak pressure measurement. In some embodiments, the
method further includes determining, using the processing unit, a
maximum negative slope occurring after the peak pressure
measurement. In some embodiments, the method further includes
determining, using the processing unit, a starting point of the
diagnostic window based on the maximum negative slope. In some
embodiments, the starting point of the diagnostic window is offset
from the maximum negative slope. In some embodiments, the method
further includes determining, using the processing unit, a further
sign change of the slope. In some embodiments, the method further
includes determining, using the processing unit, a minimum pressure
measurement based on the further sign change of the slope. In some
embodiments, the minimum pressure measurement is offset from the
further sign change of the slope. In some embodiments, the method
further includes determining, using the processing unit, an ending
point of the diagnostic window based on the minimum pressure
measurement. In some embodiments, the ending point of the
diagnostic window is offset from the minimum pressure
measurement.
[0015] In some embodiments, the method further includes introducing
a first pressure-sensing instrument into the vessel of the patient
proximal of the stenosis of the vessel; and introducing a second
pressure-sensing instrument into the vessel of the patient distal
of the stenosis of the vessel. In some embodiments, the receiving
proximal pressure measurements includes receiving proximal pressure
measurements while the first pressure-sensing instrument is
positioned within the vessel at a position proximal of the stenosis
of the vessel; and the receiving distal pressure measurements
includes receiving distal pressure measurements while the second
pressure-sensing instrument is positioned within the vessel at a
position distal of the stenosis of the vessel. In some embodiments,
the method further includes identifying a treatment option based on
the calculated pressure ratio; and performing the identified
treatment option.
[0016] Additional aspects, features, and advantages of the present
disclosure will become apparent from the following detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Illustrative embodiments of the present disclosure will be
described with reference to the accompanying drawings, of
which:
[0018] FIG. 1 is a diagrammatic perspective view of a vessel having
a stenosis according to an embodiment of the present
disclosure.
[0019] FIG. 2 is a diagrammatic, partial cross-sectional
perspective view of a portion of the vessel of FIG. 1 taken along
section line 2-2 of FIG. 1.
[0020] FIG. 3 is a diagrammatic, partial cross-sectional
perspective view of the vessel of FIGS. 1 and 2 with instruments
positioned therein according to an embodiment of the present
disclosure.
[0021] FIG. 4 is a diagrammatic, schematic view of a system
according to an embodiment of the present disclosure.
[0022] FIG. 5 is a graphical representation of measured pressure
and velocity within a vessel, annotated to identify a diagnostic
window, according to an embodiment of the present disclosure.
[0023] FIG. 6 is a graphical representation of identifying a
feature of a pressure waveform, cardiac cycle, and/or a diagnostic
window using an ECG signal.
[0024] FIG. 7 is a graphical representation of a diagnostic window
identified based on the feature of FIG. 6.
[0025] FIG. 8 is a graphical representation of a diagnostic window
identified based on the feature of FIG. 6 according to another
embodiment of the present disclosure
[0026] FIG. 9 is a graphical representation of a segment of a
pressure waveform.
[0027] FIG. 10 is a pair of graphical representations, where the
top graphical representation illustrates a segment-by-segment
analysis of the pressure waveform and the bottom graphical
representation illustrates a slope of the pressure waveform
associated with each segment.
[0028] FIG. 11 is a pair of graphical representations similar to
that of FIG. 10, but where the segment slope waveform of the bottom
graphical representation has been shifted relative the segment
slope waveform of FIG. 10.
[0029] FIG. 12 is a graphical representation of identifying a
feature of a pressure waveform, a cardiac cycle, and/or a
diagnostic window, using the segment slope waveform.
[0030] FIG. 13 is a graphical representation of identifying a
diagnostic window based on the feature of FIG. 12.
[0031] FIG. 14 is a flow diagram of a method of evaluating a vessel
of a patient.
DETAILED DESCRIPTION
[0032] For the purposes of promoting an understanding of the
principles of the present disclosure, reference will now be made to
the embodiments illustrated in the drawings, and specific language
will be used to describe the same. It is nevertheless understood
that no limitation to the scope of the disclosure is intended. Any
alterations and further modifications to the described devices,
systems, and methods, and any further application of the principles
of the present disclosure are fully contemplated and included
within the present disclosure as would normally occur to one
skilled in the art to which the disclosure relates. In particular,
it is fully contemplated that the features, components, and/or
steps described with respect to one embodiment may be combined with
the features, components, and/or steps described with respect to
other embodiments of the present disclosure. For the sake of
brevity, however, the numerous iterations of these combinations
will not be described separately.
[0033] Referring to FIGS. 1 and 2, shown therein is a vessel 100
having a stenosis according to an embodiment of the present
disclosure. In that regard, FIG. 1 is a diagrammatic perspective
view of the vessel 100, while FIG. 2 is a partial cross-sectional
perspective view of a portion of the vessel 100 taken along section
line 2-2 of FIG. 1. Referring more specifically to FIG. 1, the
vessel 100 includes a proximal portion 102 and a distal portion
104. A lumen 106 extends along the length of the vessel 100 between
the proximal portion 102 and the distal portion 104. In that
regard, the lumen 106 is configured to allow the flow of fluid
through the vessel. In some instances, the vessel 100 is a systemic
blood vessel. In some particular instances, the vessel 100 is a
coronary artery. In such instances, the lumen 106 is configured to
facilitate the flow of blood through the vessel 100.
[0034] As shown, the vessel 100 includes a stenosis 108 between the
proximal portion 102 and the distal portion 104. Stenosis 108 is
generally representative of any blockage or other structural
arrangement that results in a restriction to the flow of fluid
through the lumen 106 of the vessel 100. Embodiments of the present
disclosure are suitable for use in a wide variety of vascular
applications, including without limitation coronary, peripheral
(including but not limited to lower limb, carotid, and
neurovascular), renal, and/or venous. Where the vessel 100 is a
blood vessel, the stenosis 108 may be a result of plaque buildup,
including without limitation plaque components such as fibrous,
fibro-lipidic (fibro fatty), necrotic core, calcified (dense
calcium), blood, fresh thrombus, and mature thrombus. Generally,
the composition of the stenosis will depend on the type of vessel
being evaluated. In that regard, it is understood that the concepts
of the present disclosure are applicable to virtually any type of
blockage or other narrowing of a vessel that results in decreased
fluid flow.
[0035] Referring more particularly to FIG. 2, the lumen 106 of the
vessel 100 has a diameter 110 proximal of the stenosis 108 and a
diameter 112 distal of the stenosis. In some instances, the
diameters 110 and 112 are substantially equal to one another. In
that regard, the diameters 110 and 112 are intended to represent
healthy portions, or at least healthier portions, of the lumen 106
in comparison to stenosis 108. Accordingly, these healthier
portions of the lumen 106 are illustrated as having a substantially
constant cylindrical profile and, as a result, the height or width
of the lumen has been referred to as a diameter. However, it is
understood that in many instances these portions of the lumen 106
will also have plaque buildup, a non-symmetric profile, and/or
other irregularities, but to a lesser extent than stenosis 108 and,
therefore, will not have a cylindrical profile. In such instances,
the diameters 110 and 112 are understood to be representative of a
relative size or cross-sectional area of the lumen and do not imply
a circular cross-sectional profile.
[0036] As shown in FIG. 2, stenosis 108 includes plaque buildup 114
that narrows the lumen 106 of the vessel 100. In some instances,
the plaque buildup 114 does not have a uniform or symmetrical
profile, making angiographic evaluation of such a stenosis
unreliable. In the illustrated embodiment, the plaque buildup 114
includes an upper portion 116 and an opposing lower portion 118. In
that regard, the lower portion 118 has an increased thickness
relative to the upper portion 116 that results in a non-symmetrical
and non-uniform profile relative to the portions of the lumen
proximal and distal of the stenosis 108. As shown, the plaque
buildup 114 decreases the available space for fluid to flow through
the lumen 106. In particular, the cross-sectional area of the lumen
106 is decreased by the plaque buildup 114. At the narrowest point
between the upper and lower portions 116, 118 the lumen 106 has a
height 120, which is representative of a reduced size or
cross-sectional area relative to the diameters 110 and 112 proximal
and distal of the stenosis 108. Note that the stenosis 108,
including plaque buildup 114 is exemplary in nature and should be
considered limiting in any way. In that regard, it is understood
that the stenosis 108 has other shapes and/or compositions that
limit the flow of fluid through the lumen 106 in other instances.
While the vessel 100 is illustrated in FIGS. 1 and 2 as having a
single stenosis 108 and the description of the embodiments below is
primarily made in the context of a single stenosis, it is
nevertheless understood that the devices, systems, and methods
described herein have similar application for a vessel having
multiple stenosis regions.
[0037] Referring now to FIG. 3, the vessel 100 is shown with
instruments 130 and 132 positioned therein according to an
embodiment of the present disclosure. In general, instruments 130
and 132 may be any form of device, instrument, or probe sized and
shaped to be positioned within a vessel. In the illustrated
embodiment, instrument 130 is generally representative of a guide
wire, while instrument 132 is generally representative of a
catheter. In that regard, instrument 130 extends through a central
lumen of instrument 132. However, in other embodiments, the
instruments 130 and 132 take other forms. In that regard, the
instruments 130 and 132 are of similar form in some embodiments.
For example, in some instances, both instruments 130 and 132 are
guide wires. In other instances, both instruments 130 and 132 are
catheters. On the other hand, the instruments 130 and 132 are of
different form in some embodiments, such as the illustrated
embodiment, where one of the instruments is a catheter and the
other is a guide wire. Further, in some instances, the instruments
130 and 132 are disposed coaxial with one another, as shown in the
illustrated embodiment of FIG. 3. In other instances, one of the
instruments extends through an off-center lumen of the other
instrument. In yet other instances, the instruments 130 and 132
extend side-by-side. In some particular embodiments, at least one
of the instruments is as a rapid-exchange device, such as a
rapid-exchange catheter. In such embodiments, the other instrument
is a buddy wire or other device configured to facilitate the
introduction and removal of the rapid-exchange device. Further
still, in other instances, instead of two separate instruments 130
and 132 a single instrument is utilized. In that regard, the single
instrument incorporates aspects of the functionalities (e.g., data
acquisition) of both instruments 130 and 132 in some
embodiments.
[0038] Instrument 130 is configured to obtain diagnostic
information about the vessel 100. In that regard, the instrument
130 includes one or more sensors, transducers, and/or other
monitoring elements configured to obtain the diagnostic information
about the vessel. The diagnostic information includes one or more
of pressure, flow (velocity), images (including images obtained
using ultrasound (e.g., IVUS), OCT, thermal, and/or other imaging
techniques), temperature, and/or combinations thereof. The one or
more sensors, transducers, and/or other monitoring elements are
positioned adjacent a distal portion of the instrument 130 in some
instances. In that regard, the one or more sensors, transducers,
and/or other monitoring elements are positioned less than 30 cm,
less than 10 cm, less than 5 cm, less than 3 cm, less than 2 cm,
and/or less than 1 cm from a distal tip 134 of the instrument 130
in some instances. In some instances, at least one of the one or
more sensors, transducers, and/or other monitoring elements is
positioned at the distal tip of the instrument 130.
[0039] The instrument 130 includes at least one element configured
to monitor pressure within the vessel 100. The pressure monitoring
element can take the form a piezo-resistive pressure sensor, a
piezo-electric pressure sensor, a capacitive pressure sensor, an
electromagnetic pressure sensor, a fluid column (the fluid column
being in communication with a fluid column sensor that is separate
from the instrument and/or positioned at a portion of the
instrument proximal of the fluid column), an optical pressure
sensor, and/or combinations thereof. In some instances, one or more
features of the pressure monitoring element are implemented as a
solid-state component manufactured using semiconductor and/or other
suitable manufacturing techniques. Examples of commercially
available guide wire products that include suitable pressure
monitoring elements include, without limitation, the PrimeWire
PRESTIGE.RTM. pressure guide wire, the PrimeWire.RTM. pressure
guide wire, and the ComboWire.RTM. XT pressure and flow guide wire,
each available from Volcano Corporation, as well as the
PressureWire.TM. Certus guide wire and the PressureWire.TM. Aeris
guide wire, each available from St. Jude Medical, Inc. Generally,
the instrument 130 is sized such that it can be positioned through
the stenosis 108 without significantly impacting fluid flow across
the stenosis, which would impact the distal pressure reading.
Accordingly, in some instances the instrument 130 has an outer
diameter of 0.018'' or less. In some embodiments, the instrument
130 has an outer diameter of 0.014'' or less.
[0040] Instrument 132 is also configured to obtain diagnostic
information about the vessel 100. In some instances, instrument 132
is configured to obtain the same diagnostic information as
instrument 130. In other instances, instrument 132 is configured to
obtain different diagnostic information than instrument 130, which
may include additional diagnostic information, less diagnostic
information, and/or alternative diagnostic information. The
diagnostic information obtained by instrument 132 includes one or
more of pressure, flow (velocity), images (including images
obtained using ultrasound (e.g., IVUS), OCT, thermal, and/or other
imaging techniques), temperature, and/or combinations thereof.
Instrument 132 includes one or more sensors, transducers, and/or
other monitoring elements configured to obtain this diagnostic
information. In that regard, the one or more sensors, transducers,
and/or other monitoring elements are positioned adjacent a distal
portion of the instrument 132 in some instances. In that regard,
the one or more sensors, transducers, and/or other monitoring
elements are positioned less than 30 cm, less than 10 cm, less than
5 cm, less than 3 cm, less than 2 cm, and/or less than 1 cm from a
distal tip 136 of the instrument 132 in some instances. In some
instances, at least one of the one or more sensors, transducers,
and/or other monitoring elements is positioned at the distal tip of
the instrument 132.
[0041] Similar to instrument 130, instrument 132 also includes at
least one element configured to monitor pressure within the vessel
100. The pressure monitoring element can take the form a
piezo-resistive pressure sensor, a piezo-electric pressure sensor,
a capacitive pressure sensor, an electromagnetic pressure sensor, a
fluid column (the fluid column being in communication with a fluid
column sensor that is separate from the instrument and/or
positioned at a portion of the instrument proximal of the fluid
column), an optical pressure sensor, and/or combinations thereof.
In some instances, one or more features of the pressure monitoring
element are implemented as a solid-state component manufactured
using semiconductor and/or other suitable manufacturing techniques.
Millar catheters are utilized in some embodiments. Currently
available catheter products suitable for use with one or more of
Philips's Xper Flex Cardio Physiomonitoring System, GE's Mac-Lab XT
and XTi hemodynamic recording systems, Siemens's AXIOM Sensis XP
VC11, McKesson's Horizon Cardiology Hemo, and Mennen's Horizon XVu
Hemodynamic Monitoring System and include pressure monitoring
elements can be utilized for instrument 132 in some instances.
[0042] In accordance with aspects of the present disclosure, at
least one of the instruments 130 and 132 is configured to monitor a
pressure within the vessel 100 distal of the stenosis 108 and at
least one of the instruments 130 and 132 is configured to monitor a
pressure within the vessel proximal of the stenosis. In that
regard, the instruments 130, 132 are sized and shaped to allow
positioning of the at least one element configured to monitor
pressure within the vessel 100 to be positioned proximal and/or
distal of the stenosis 108 as necessary based on the configuration
of the devices. In that regard, FIG. 3 illustrates a position 138
suitable for measuring pressure distal of the stenosis 108. In that
regard, the position 138 is less than 5 cm, less than 3 cm, less
than 2 cm, less than 1 cm, less than 5 mm, and/or less than 2.5 mm
from the distal end of the stenosis 108 (as shown in FIG. 2) in
some instances. FIG. 3 also illustrates a plurality of suitable
positions for measuring pressure proximal of the stenosis 108. In
that regard, positions 140, 142, 144, 146, and 148 each represent a
position that is suitable for monitoring the pressure proximal of
the stenosis in some instances. In that regard, the positions 140,
142, 144, 146, and 148 are positioned at varying distances from the
proximal end of the stenosis 108 ranging from more than 20 cm down
to about 5 mm or less. Generally, the proximal pressure measurement
will be spaced from the proximal end of the stenosis. Accordingly,
in some instances, the proximal pressure measurement is taken at a
distance equal to or greater than an inner diameter of the lumen of
the vessel from the proximal end of the stenosis. In the context of
coronary artery pressure measurements, the proximal pressure
measurement is generally taken at a position proximal of the
stenosis and distal of the aorta, within a proximal portion of the
vessel. However, in some particular instances of coronary artery
pressure measurements, the proximal pressure measurement is taken
from a location inside the aorta. In other instances, the proximal
pressure measurement is taken at the root or ostium of the coronary
artery.
[0043] Referring now to FIG. 4, shown therein is a system 150
according to an embodiment of the present disclosure. In that
regard, FIG. 4 is a diagrammatic, schematic view of the system 150.
As shown, the system 150 includes an instrument 152. In that
regard, in some instances instrument 152 is suitable for use as at
least one of instruments 130 and 132 discussed above. Accordingly,
in some instances the instrument 152 includes features similar to
those discussed above with respect to instruments 130 and 132 in
some instances. In the illustrated embodiment, the instrument 152
is a guide wire having a distal portion 154 and a housing 156
positioned adjacent the distal portion. In that regard, the housing
156 is spaced approximately 3 cm from a distal tip of the
instrument 152. The housing 156 is configured to house one or more
sensors, transducers, and/or other monitoring elements configured
to obtain the diagnostic information about the vessel. In the
illustrated embodiment, the housing 156 contains at least a
pressure sensor configured to monitor a pressure within a lumen in
which the instrument 152 is positioned. A shaft 158 extends
proximally from the housing 156. A torque device 160 is positioned
over and coupled to a proximal portion of the shaft 158. A proximal
end portion 162 of the instrument 152 is coupled to a connector
164. A cable 166 extends from connector 164 to a connector 168. In
some instances, connector 168 is configured to be plugged into an
interface 170. In that regard, interface 170 is a patient interface
module (PIM) in some instances. In some instances, the cable 166 is
replaced with a wireless connection. In that regard, it is
understood that various communication pathways between the
instrument 152 and the interface 170 may be utilized, including
physical connections (including electrical, optical, and/or fluid
connections), wireless connections, and/or combinations
thereof.
[0044] The interface 170 is communicatively coupled to a computing
device 172 via a connection 174. Computing device 172 is generally
representative of any device suitable for performing the processing
and analysis techniques discussed within the present disclosure. In
some embodiments, the computing device 172 includes a processor,
random access memory, and a storage medium. In that regard, in some
particular instances the computing device 172 is programmed to
execute steps associated with the data acquisition and analysis
described herein. Accordingly, it is understood that any steps
related to data acquisition, data processing, instrument control,
and/or other processing or control aspects of the present
disclosure may be implemented by the computing device using
corresponding instructions stored on or in a non-transitory
computer readable medium accessible by the computing device. In
some instances, the computing device 172 is a console device. In
some particular instances, the computing device 172 is similar to
the s5.TM. Imaging System or the s5i.TM. Imaging System, each
available from Volcano Corporation. In some instances, the
computing device 172 is portable (e.g., handheld, on a rolling
cart, etc.). Further, it is understood that in some instances the
computing device 172 comprises a plurality of computing devices. In
that regard, it is particularly understood that the different
processing and/or control aspects of the present disclosure may be
implemented separately or within predefined groupings using a
plurality of computing devices. Any divisions and/or combinations
of the processing and/or control aspects described below across
multiple computing devices are within the scope of the present
disclosure.
[0045] Together, connector 164, cable 166, connector 168, interface
170, and connection 174 facilitate communication between the one or
more sensors, transducers, and/or other monitoring elements of the
instrument 152 and the computing device 172. However, this
communication pathway is exemplary in nature and should not be
considered limiting in any way. In that regard, it is understood
that any communication pathway between the instrument 152 and the
computing device 172 may be utilized, including physical
connections (including electrical, optical, and/or fluid
connections), wireless connections, and/or combinations thereof. In
that regard, it is understood that the connection 174 is wireless
in some instances. In some instances, the connection 174 includes a
communication link over a network (e.g., intranet, internet,
telecommunications network, and/or other network). In that regard,
it is understood that the computing device 172 is positioned remote
from an operating area where the instrument 152 is being used in
some instances. Having the connection 174 include a connection over
a network can facilitate communication between the instrument 152
and the remote computing device 172 regardless of whether the
computing device is in an adjacent room, an adjacent building, or
in a different state/country. Further, it is understood that the
communication pathway between the instrument 152 and the computing
device 172 is a secure connection in some instances. Further still,
it is understood that, in some instances, the data communicated
over one or more portions of the communication pathway between the
instrument 152 and the computing device 172 is encrypted.
[0046] The system 150 also includes an instrument 175. In that
regard, in some instances instrument 175 is suitable for use as at
least one of instruments 130 and 132 discussed above. Accordingly,
in some instances the instrument 175 includes features similar to
those discussed above with respect to instruments 130 and 132 in
some instances. In the illustrated embodiment, the instrument 175
is a catheter-type device. In that regard, the instrument 175
includes one or more sensors, transducers, and/or other monitoring
elements adjacent a distal portion of the instrument configured to
obtain the diagnostic information about the vessel. In the
illustrated embodiment, the instrument 175 includes a pressure
sensor configured to monitor a pressure within a lumen in which the
instrument 175 is positioned. The instrument 175 is in
communication with an interface 176 via connection 177. In some
instances, interface 176 is a hemodynamic monitoring system or
other control device, such as Siemens AXIOM Sensis, Mennen Horizon
XVu, and Philips Xper IM Physiomonitoring 5. In one particular
embodiment, instrument 175 is a pressure-sensing catheter that
includes fluid column extending along its length. In such an
embodiment, interface 176 includes a hemostasis valve fluidly
coupled to the fluid column of the catheter, a manifold fluidly
coupled to the hemostasis valve, and tubing extending between the
components as necessary to fluidly couple the components. In that
regard, the fluid column of the catheter is in fluid communication
with a pressure sensor via the valve, manifold, and tubing. In some
instances, the pressure sensor is part of interface 176. In other
instances, the pressure sensor is a separate component positioned
between the instrument 175 and the interface 176. The interface 176
is communicatively coupled to the computing device 172 via a
connection 178.
[0047] Similar to the connections between instrument 152 and the
computing device 172, interface 176 and connections 177 and 178
facilitate communication between the one or more sensors,
transducers, and/or other monitoring elements of the instrument 175
and the computing device 172. However, this communication pathway
is exemplary in nature and should not be considered limiting in any
way. In that regard, it is understood that any communication
pathway between the instrument 175 and the computing device 172 may
be utilized, including physical connections (including electrical,
optical, and/or fluid connections), wireless connections, and/or
combinations thereof. In that regard, it is understood that the
connection 178 is wireless in some instances. In some instances,
the connection 178 includes a communication link over a network
(e.g., intranet, internet, telecommunications network, and/or other
network). In that regard, it is understood that the computing
device 172 is positioned remote from an operating area where the
instrument 175 is being used in some instances. Having the
connection 178 include a connection over a network can facilitate
communication between the instrument 175 and the remote computing
device 172 regardless of whether the computing device is in an
adjacent room, an adjacent building, or in a different
state/country. Further, it is understood that the communication
pathway between the instrument 175 and the computing device 172 is
a secure connection in some instances. Further still, it is
understood that, in some instances, the data communicated over one
or more portions of the communication pathway between the
instrument 175 and the computing device 172 is encrypted.
[0048] It is understood that one or more components of the system
150 are not included, are implemented in a different
arrangement/order, and/or are replaced with an alternative
device/mechanism in other embodiments of the present disclosure.
For example, in some instances, the system 150 does not include
interface 170 and/or interface 176. In such instances, the
connector 168 (or other similar connector in communication with
instrument 152 or instrument 175) may plug into a port associated
with computing device 172. Alternatively, the instruments 152, 175
may communicate wirelessly with the computing device 172. Generally
speaking, the communication pathway between either or both of the
instruments 152, 175 and the computing device 172 may have no
intermediate nodes (i.e., a direct connection), one intermediate
node between the instrument and the computing device, or a
plurality of intermediate nodes between the instrument and the
computing device.
[0049] In some embodiments of the present disclose, a ratio of
intravascular pressure measurements obtained during a portion of
the heartbeat cycle or diagnostic window is calculated. For
example, FIG. 5 includes graphical representation 220 having a plot
222 representative of pressure (measured in mmHg) within a vessel
over the time period of one cardiac cycle and a plot 224
representative of velocity (measured in m/s) of a fluid within the
vessel over the same cardiac cycle. FIG. 5 is annotated to identify
a diagnostic window 236. The diagnostic window identifies a portion
of the heartbeat cycle of the patient where the resistance (e.g.,
pressure divided by velocity) within vasculature is reduced without
the use of a hyperemic agent or other stressing technique. That is,
the diagnostic window 236 corresponds to a portion of the heartbeat
cycle of a resting patient that has a naturally reduced and
relatively constant resistance.
[0050] The portion of the heartbeat cycle coinciding with the
diagnostic window 236 can be utilized to evaluate a stenosis of the
vessel of a patient without the use of a hyperemic agent or other
stressing of the patient's heart. In particular, the pressure ratio
(e.g., distal pressure divided by proximal pressure) across the
stenosis is calculated for the time period corresponding to the
diagnostic window 236 for one or more heartbeats. The calculated
pressure ratio is an average over the diagnostic window in some
instances. By comparing the calculated pressure ratio to a
threshold or predetermined value, a physician or other treating
medical personnel can determine what, if any, treatment should be
administered. In that regard, in some instances, a calculated
pressure ratio above a threshold value (e.g., 0.80 on a scale of
0.00 to 1.00) is indicative of a first treatment mode (e.g., no
treatment, drug therapy, etc.), while a calculated pressure ratio
below the threshold value is indicative of a second, more invasive
treatment mode (e.g., angioplasty, stent, etc.). In some instances,
the threshold value is a fixed, preset value. In other instances,
the threshold value is selected for a particular patient and/or a
particular stenosis of a patient. In that regard, the threshold
value for a particular patient may be based on one or more of
empirical data, patient characteristics, patient history, physician
preference, available treatment options, and/or other parameters.
Various aspects of the diagnostic window, including identification
of the diagnostic window, features of the diagnostic window, etc.,
are described in U.S. application Ser. No. 13/460,296, titled
"Devices, Systems, and Methods for Assessing a Vessel," and filed
Apr. 30, 2012, the entirety of which is incorporated by reference
herein.
[0051] Referring now to FIGS. 6-8, shown therein are various
graphical representations of techniques for determining start
and/or end points for a diagnostic window in conjunction with an
ECG signal in accordance with the present disclosure. The graphical
representation 700 of FIG. 6 illustrates a proximal pressure
waveform 302, a distal pressure waveform 304, and an associated ECG
waveform 705. The proximal pressure waveform 302 and distal
pressure waveform 304 are representative of proximal and distal
pressure measurements obtained within the vasculature. The ECG
waveform 705 is representative of an ECG signal of the patient
obtained at the same time as the proximal and distal pressure
measurements are obtained. In that regard, the waveforms 302, 304,
705 in FIGS. 6-8 are arranged to show how the illustrated
physiological attributes are generally aligned in time.
[0052] Referring again to FIG. 6, a computing device can identify
feature(s) of a diagnostic window, pressure waveform(s) 302, 304,
and/or the patient's cardiac cycle based on the ECG waveform 705.
For example, using the peak of the R-wave in the ECG waveform 705,
the computing device can identify a minimum pressure value or
valley 701, 703 for each cardiac cycle. In particular, the peak of
the R-wave in the ECG waveform 705 occurs at a time 702 that
corresponds to the minimum pressure value 701 in the distal
pressure waveform 304. The next peak of the R-wave in the ECG
waveform 705 (for the next cardiac cycle) occurs at a time 704 that
corresponds to the minimum pressure value 703 in the distal
pressure waveform 304. In that regard, the minimum pressure value
701 corresponds to a cardiac cycle (n), and the minimum pressure
value 703 corresponds to a next cardiac cycle (n+1). The time 702
corresponds to the beginning of the cardiac cycle (n) and/or the
beginning of systole (n). The time 704 corresponds to the end of
the cardiac cycle (n), beginning of the next cardiac cycle (n+1),
the end of diastole (n), and/or the beginning of systole (n+1).
While the distal pressure waveform 304 is specifically mentioned in
this discussion, it is understood that the proximal pressure
waveform 302 can be similarly utilized. Generally, at least one
identifiable feature of the ECG signal (including without
limitation, the start of a P-wave, the peak of a P-wave, the end of
a P-wave, a PR interval, a PR segment, the beginning of a QRS
complex, the start of an R-wave, the peak of an R-wave, the end of
an R-wave, the end of a QRS complex (J-point), an ST segment, the
start of a T-wave, the peak of a T-wave, and the end of a T-wave)
can utilized to select that starting point and/or ending point of
the diagnostic window, identify features of the proximal or distal
pressure waveforms 302, 304, etc., as described for example, in
U.S. application Ser. No. 13/460,296, titled "Devices, Systems, and
Methods for Assessing a Vessel," and filed Apr. 30, 2012, the
entirety of which is incorporated by reference herein.
[0053] Referring now to FIG. 7, shown therein is a graphical
representation 711 of selecting a diagnostic window based on the
feature(s) of the pressure waveform(s) identified using the ECG
signal. In some instances, the starting point 710 and/or ending
point 714 of the diagnostic window 716 is determined by adding or
subtracting a fixed amount of time 708, 712 to an identifiable
feature of the ECG signal. In that regard, the fixed amount time
708, 712 can be a percentage of the cardiac cycle 706 in some
instances. In that regard, the diagnostic window or wave-free
period 716 can be identified based on the minimum pressure values
701, 703. For example, the time period 706 between the minimum
pressure values 701, 703 corresponds to the duration of a cardiac
cycle. A computing device can select a beginning point 710 of the
diagnostic window 716 to be positioned a fixed percentage of the
total cardiac cycle time 706 from the time 702. That is, the
beginning point 710 of the diagnostic window can be offset by a
period 708 from the time 702 of the minimum pressure value 701. A
computing device can select an ending point 714 of the diagnostic
window 716 to be positioned a fixed percentage of the total cardiac
cycle time 706 from the time 704. That is, the ending point 714 of
the diagnostic window can be offset by a period 712 from the time
704 of the next minimum pressure value 703. One, the other, or both
of the periods 708, 712 can be described as a percentage of the
total cardiac cycle time 706, including values between about 5% and
about 95%, between about 10% and about 50%, between about 20% and
40%, such as 15%, 20%, 25%, 30%, 35%, 40%, and/or other suitable
values both larger and smaller.
[0054] Referring now to FIG. 8, shown therein is a graphical
representation 721 of selecting a diagnostic window based on the
feature(s) of the pressure waveform(s) identified using the ECG
signal, according to another embodiment of the present disclosure.
In that regard, the diagnostic window or wave-free period 732 can
be identified based on the minimum pressure values 701, 703.
Starting from the minimum pressure value 701, a computing device
can identify a peak pressure value 720 in the distal pressure
waveform 304. The computing device can identify a maximum
negative/down slope value 722 that occurs after the peak pressure
value 720. The maximum negative/down slope value 722 identifies
when the pressure waveform 304 decreases at the fastest rate. The
diagnostic window 732 can be selected within the period 734 between
the maximum down slope value 722 and the next minimum pressure
value 703. In that regard, the computing device can select a
beginning point 726 of the diagnostic window 732 to be positioned a
fixed percentage of the period 734 from the time 723. That is, the
beginning point 726 of the diagnostic window can be offset by a
period 724 from the time 723 of the maximum down slope value 722. A
computing device can select an ending point 730 of the diagnostic
window 732 to be positioned a fixed percentage of the period 734
from the time 704. That is, the ending point 730 of the diagnostic
window can be offset by a period 728 from the time 704 of the next
minimum pressure value 703. One, the other, or both of the periods
724, 728 can be described as a percentage of the period 734,
including values between about 10% and about 90%, between about 12%
and about 40%, between about 15% and 30%, such as 15%, 20%, 25%,
and/or other suitable values both larger and smaller. For example,
the period 724 can be 25% of the period 734, and the period 728 can
be 15% of the period 734.
[0055] Referring now to FIGS. 9-14, shown therein are various
graphical representations of techniques for determining start
and/or end points for a diagnostic window. In particular, the
algorithm described in the FIGS. 9-14 uses a segment-by-segment
analysis of the pressure waveform(s) to identify feature(s) of the
cardiac cycle (e.g., the beginning/ending of a cardiac cycle)
and/or the pressure waveform(s) themselves (e.g., a minimum
pressure value, a peak pressure value, etc.). The diagnostic window
is then selected based on the identified feature(s). In that
regard, an ECG signal is not used to identify the diagnostic
window, a feature of the pressure waveform(s), and/or a feature of
the cardiac cycle. Thus, any discomfort experienced by the patient
associated with obtaining the ECG signal can be advantageously
avoided.
[0056] Referring now to FIG. 9, shown therein is a graphical
representation 731 of a distal pressure waveform 705. As described
herein, the waveform 705 is a based on distal pressure measurements
obtained by an intravascular device disposed within vasculature.
While a distal pressure waveform is specifically referenced in this
discussion, it is understood that a proximal pressure waveform can
be similarly utilized. Additionally, while the waveforms in FIG. 9
and elsewhere are shown as smooth, it is understood that the
waveforms comprise discrete pressure measurement(s).
[0057] A segment 740a of the pressure waveform 705 is indicated in
FIG. 9. The segment 740a identifies a portion of the pressure
waveform 705, a subset of the pressure measurements associated with
the pressure waveform 705, and/or a time period associated with the
pressure waveform 705. As described herein, a period-by-period or
segment-by-segment analysis is used to identify features of the
cardiac cycle and/or the pressure waveform itself. In some
instances, time period, period, and/or segment may be used
interchangeably in the discussion herein. The time period or
segment 740a has a segment width (SW). That is, the pressure
measurements associated with the segment 740a are obtained over the
given time. For example, the width or duration of the segment 740a
can be less than a cardiac cycle duration, encompassing only a
portion of the cardiac cycle. In various embodiments, the duration
of the segment 740a compared to the cardiac cycle duration is
between approximately 10% and approximately 90%, approximately 10%
and approximately 50%, approximately 10% and approximately 40%,
including values such as 20%, 25%, 30%, 33%, 35%, and/or other
suitable values both larger and smaller. In some instances, a
cardiac cycle duration can be approximately 1 second. For example,
the duration of the segment 740a can be between approximately 0.1
seconds and approximately 0.9 seconds, approximately 0.1 seconds
and approximately 0.5 seconds, approximately 0.1 seconds and
approximately 0.4 seconds, including values such as 0.2 seconds,
0.25 seconds, 0.3 seconds, 0.33 seconds, 0.35 seconds, and/or other
suitable values both larger and smaller. In some embodiments, the
width or duration of the segment 740a varies for each cardiac
cycle. For example, time periods associated with different cardiac
cycles have different durations. In that regard, the duration of
the segment 740a can be adjusted manually by a user or
automatically by a computing device. For example, the duration of
the segment 740a can be based on the cardiac cycle duration of the
cardiac cycle. In that regard, the cardiac cycle duration can be
described as the duration between consecutive peak pressure values,
consecutive minimum pressure values, etc. For example, the duration
of the segment 740a of a cardiac cycle (n) can be based on the
duration of one or more earlier cardiac cycles (n-1, n-2, etc.)
such that the duration is adaptive to a patient's heart rhythm. In
some embodiments, a duration of the time periods is based on a
duration of time periods in one or more previous cardiac cycles.
For example, the duration of the segment 740a can an average of
earlier segment durations. That is, the duration of segment 740a
can be the average of multiple, prior segment durations. The number
of prior segments considered can be variable, adjustable manually
by a user, and/or adjustable automatically be a computing device.
In some embodiments, the width or duration of the segment 740a can
be defined by a quantity of pressure measurements obtained during
the segment. In some embodiments, the duration of the segment 740a
is bounded by a maximum duration and a minimum duration. In some
embodiments, the duration of the segment 740a (e.g., relative to a
cardiac cycle) is optimized during manufacture of an intravascular
system, while in other embodiments, the duration of the segment can
be adjusted prior to, during, and/or after an intravascular
procedure.
[0058] Referring now to FIG. 10, shown therein is a graphical
representation 751 illustrating a period-by-period analysis of the
pressure waveform 705. Also shown is a segment slope waveform 707
illustrating a slope of the pressure waveform 705 associated with
each segment. According to an aspect of the present disclosure, a
period-by-period analysis of the slope of the pressure waveform 705
is used to identify feature(s) of the cardiac cycle (e.g., the
beginning/ending of a cardiac cycle) and/or the pressure
waveform(s) itself (e.g., a minimum pressure value, a peak pressure
value, etc.). Generally, specific patterns exist within arterial
blood pressure waveforms. The patterns, such as maxima (peaks) and
minima (valleys) of the pressure waveforms, can be used to identify
the cardiac cycle and the wave-free diagnostic period within the
cardiac cycle. In the case of healthy vasculature with a regular
cardiac cycle, there are minimal artifacts in the pressure signals.
Thus, the peaks and valleys of the pressure waveforms can be
detected by simply finding the minimum and the maximum values,
without the aid of massive filtering processes. However, the
pressure signals from diseased hearts are typically distorted by
abnormal heart operations (e.g., arrhythmia, premature ventricular
contraction, etc.) and/or motion artifacts resulting from pressure
measurement (e.g., pullback of the pressure-sensing intravascular
device). Therefore, complicated filtering procedures are typically
needed to remove those corruptions and to have clean pressure
signals from which to visualize peaks and valleys clearly. In that
regard, the algorithm described herein advantageously provides for
robust identification of features of the cardiac cycle and/or
pressure waveform, even in diseased vasculature and without the
need for extensive signal filtering hardware or software.
[0059] FIG. 10 illustrates a plurality of period segments 740a,
740b, 740c. It is understood the segments 740a-740c are only a
portion of the total number of segments used to analyze pressure
waveform 705. In some embodiments, the width or duration of each
segment 740a-740c is the same for a given cardiac cycle. For
example, time periods associated with a single cardiac cycle have
the same duration. In some embodiments, the each of the segments
740a-740c are consecutive or adjacent in time. For example, a
beginning point, midpoint, and/or ending point of the segments
740a, 740b, 740c can be adjacent in time. For example, every
subsequent pressure sample may define the beginning of a different
segment. Each of the segments 740a-740c can be defined by a
starting time, ending time, and/or midpoint time. Consecutive
segments can be separated by a period between about 0.001 seconds
and about 0.5 seconds, about 0.001 seconds and 0.1 seconds,
and/other suitable values both larger and smaller, including the
time between consecutive pressure measurements. In some
embodiments, a starting point of consecutive time periods or
segments can be offset based on an acquisition rate of an
intravascular pressure-sensing device. For example, data can be
acquired from the pressure-sensing instrument for 1 ms every 5 ms
and/or other suitable rates. Consecutive time periods can be offset
by about 5 ms in such embodiments and/or other suitable times in
different embodiments. In some embodiments, the segments 740a-740c
are overlapping in time. In that regard, the segments 740a-740c can
overlap by any suitable amount of time. In some embodiments, the
time period associated with the overlap can be adjusted manually by
a user or automatically by a computing device. In some embodiments,
the overlap can be defined by a quantity of pressure measurements.
It is understood that the overlap between segments 740a-740c
illustrated in FIG. 10 is exemplary, and other overlap times, both
larger and smaller, are contemplated.
[0060] The segment slope waveform 707 is a plot of the slope of
each time period or segment (such as segments 740a-740c) of the
pressure waveform 705. In some embodiments, a computing device can
calculate the slope of the pressure waveform 705 calculated at each
pressure sample. The slope may be an average slope of the segment,
an instantaneous slope of the segment (e.g., at the beginning
point, a midpoint, and/or the ending point), and/or other suitable
quantity. For the example, the slope may be calculated as a
change/difference in two pressure measurements divided by the
change/difference in time between the two pressure measurements. In
that regard, with a sufficiently wide segment width and with an
average slope calculated across the entire duration of the segment,
the slope is advantageously less sensitive to the distorted high
and low frequency peaks resulting from abnormal vasculature
conditions or motion artifacts from pressure measurements. In some
embodiments, the sample location where the average slope is
calculated is at or near the sample in the middle of the segment.
For example, the average slope, at the midpoint of the segment, may
be calculated as the change/difference in the pressure measurement
between the starting point and the ending point of the segment
divided by the change/difference in time between the starting and
ending points. As illustrated in FIG. 10, the value of the segment
slope waveform 707 changes along the pressure waveform 705 as,
e.g., the average slope of each segment of the pressure waveform
705 is determined. In some instances, the sign or polarity of the
segment slope waveform 707 switches between positive and negative
(or vice versa).
[0061] The slope of multiple time periods or segments 745a, 745b,
745c, 745d, 745e, 745f is also illustrated in FIG. 10. In that
regard, each of the segments 745a-745f is represented by a linear
segment spanning its associated pressure measurements on the
pressure waveform 705. That is, the length of the linear segments
can correspond to the duration or width of the segments 745a-745f.
As described with respect to segments 740a-740c, for a given
cardiac cycle, the segments 745a-745f have equal width or span the
same amount of time. The linear segments are also shown as angled
to match the average slope associated with the segments 745a-745f.
For example, the segment 745a spans a portion of the pressure
waveform 705 having a generally positive slope. Correspondingly,
the linear segment for segment 745a is shown having a generally
positive slope. Segments 745b-745f variously span different
portions the pressure waveform 705 that having positive slope, zero
slope, and/or negative slope. As the influence of the zero slope or
negative slope portions increases (towards the right of pressure
waveform 705), the linear segments are illustrated as having less
positive slope than segment 745a. For example, segments 745b, 745c
span portions of the pressure waveform 705 having zero slope and
negative slope. Thus, the linear segment associated with segments
745b, 745c have a less positive slope, compared to the linear
segment associated with segment 745a, which only spans portions of
the pressure waveform 705 having positive slope. Segment 745d spans
portions of the pressure waveform 705 with an average slope of
zero. Thus, the linear segment is illustrated as having zero slope.
Segments 745e and 745f span relatively larger portions of the
pressure waveform 705 with negative slope, and, thus, the
corresponding linear segments have negative slopes. The
corresponding slope values are plotted in the segment slope
waveform 707. Generally, the slope of the segments 745a-745f
changes in the direction indicated by arrow 713. The portion of the
pressure waveform 705 spanned by the segments 745a-745f includes a
change in slope sign. This is illustrated by the linear segments
for segments 745a-745f changing slope from positive to negative.
Likewise, the segment slope waveform 707 corresponding to the area
of segments 745a-745f starts positive, crosses the zero line, and
becomes negative.
[0062] Referring now to FIG. 11, shown therein is a graphical
representation 751 including the pressure waveform 705 and segment
slope waveform 707, similar to that of graphical representation 741
(FIG. 10). Graphical representation 751 also includes a segment
slope waveform 709 that is offset from the segment slope waveform
707 by a period 742. In that regard, the period 742 can correspond
to a calculation delay in embodiments in which the segment slope is
calculated around the pressure sample at or near middle of the
segment 740a. Thus, in such embodiments, the first segment slope is
calculated only after approximately half of the duration of the
segment 740a. In general, the period 742 can be described as a
multiple of the segment width (a*SW). In that regard, the multiple
can be greater than, equal to, or less than one (a>1, a=1, or
a<1) in different embodiments. For example, the multiple (a) can
be between about 0.01 and about 0.99, about 0.1 and about 0.9,
about 0.3 and about 0.7, including values such as 0.35, 0.4, 0.45,
0.5, 0.55, 0.6, 0.65, and/or other suitable values both larger and
smaller. FIG. 11 illustrates that values of the segment slope
waveform 707 can be shifted to account for the calculation delay.
For example, the slope 744a is shifted in the direction 743 by a
time equaling the period 742, which yields the slope 744b. The
shifted segment slope waveform 709 results when all values for the
segment slope waveform 707 are similarly modified. In some
embodiments, the algorithm described herein that identifies
features of the diagnostic window, cardiac cycle, and/or the
pressure waveform utilizes the shifted waveform 709.
[0063] Referring now to FIG. 12, shown therein a graphical
representation 761 including the pressure waveform 705 and the
segment slope waveform 709. Also illustrated is a feature plot 711,
identifying when minima (valley) and maxima (peak) of the pressure
waveform 705 occur. In that regard, the waveforms 705, 709, 711 in
FIG. 12 and elsewhere are arranged show alignment in time or the
simultaneous occurrence of one or more physiological attributes.
According to aspects of the present disclosure, the minima 762, 766
and maxima 764, 768 of the pressure waveform 705 are identified
based on when the sign changes in segment slope waveform 709. The
minima 762 (n-1) of the pressure waveform 705 can correspond to the
beginning of the cardiac cycle (n-1) and/or the beginning of
systole (n-1). The next minima 766 (n) can correspond to the end of
the cardiac cycle (n-1), the end of diastole (n-1), the beginning
of the cardiac cycle (n), and/or the beginning of systole (n).
Thus, the features of the cardiac cycle can also be identified
based on when sign changes in segment slope waveform 709.
Correspondingly, the diagnostic window (e.g., the beginning, the
ending, etc.) can be selected based on when the sign changes in
segment slope waveform 709.
[0064] The sign of the segment slope waveform 709 changes at times
747, 749, 753, 755. In particular, the sign of the segment slope
waveform 709 changes from positive to negative at times 747 and
753. The locations 746, 750 in segment slope waveform 709
correspond to these positive to negative sign changes. The minima
762, 766 of the pressure waveform 705 can be identified based on
the location the sign of the segment slope waveform 709 changes
from positive to negative. For example, the minimum 762 can occur
at a time 763, prior to the time 747 associated with the sign
change 746. In an embodiment, the time 763 occurs at half of the
segment width before the time 747. Thus, the minimum 762 is offset
from the sign change 746. Generally, the period 754 separating the
positive-to-negative sign change and the minimum pressure
measurement can be a multiple of the segment width (b*SW). In that
regard, the multiple can be greater than, equal to, or less than
one (b>1, b=1, or b<1) in different embodiments. For example,
the multiple (c) can be between about 0.01 and about 2, about 0.1
and about 0.9, about 0.3 and about 0.7, including values such as
0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, and/or other suitable values
both larger and smaller. Similarly, the minimum 766 can occur at a
time 767, prior to the time 753 associated with the sign change
750. Thus, the minimum 766 is offset from the sign change 750. The
period 758 separating the times 753, 767 can be a multiple of the
segment width. In that regard, because the minima 762, 766 are
associated with different heart beat cycles, the periods 754, 758
can be different in some instances.
[0065] The value of the segment slope waveform 709 changes from
negative to positive at times 749 and 755. The locations 748, 752
in segment slope waveform 709 correspond to these
negative-to-positive sign changes. The maxima 764, 768 of the
pressure waveform 705 can be identified based on the location the
sign of the segment slope waveform 709 changes from negative to
positive. For example, the maximum 764 can occur at a time 765,
prior to the time 749 associated with the sign change 748. In an
embodiment, the time 765 occurs at 125% of the segment width before
the time 749. Thus, the maximum 764 can be offset from the sign
change 748. Generally, the period 756 separating the
negative-to-positive sign change and the peak pressure measurement
can be a multiple of the segment width (c*SW). In that regard, the
multiple can be greater than, equal to, or less than one (c>1,
c=1, or c<1) in different embodiments. For example, the multiple
(c) can be between about 0.1 and about 2, about 1 and about 2,
about 1.1 and about 1.5, including values such as 1.1, 1.2, 1.25,
1.3, 1.35, 1.4, and/or other suitable values both larger and
smaller. Similarly, the maximum 768 can occur at a time 775, prior
to the time 755 associated with the sign change 752. Thus, the
maximum 768 can be offset from the sign change 752. The period 760
separating the times 755, 775 is a multiple of the segment width.
In the regard, because the maxima 764, 768 are associated with
different heart beat cycles, the periods 756, 760 can be different
in some instances.
[0066] The feature plot 711 illustrates the location of the minima
(valley) and maxima (peak) of the pressure waveform 705. In that
regard, the valley (n-1) 770, associated with a cardiac cycle
(n-1), is aligned with the time 763 that occurs a period 754 before
the positive-to-negative sign change 746. The valley (n) 774,
associated with the next cardiac cycle (n), is aligned with the
time 767 that occurs a period 758 before the positive-to-negative
sign change 750. The peak (n-1) 764, associated with a cardiac
cycle (n-1), is aligned with the time 765 that occurs a period 756
before the negative-to-positive sign change 748. The peak (n) 768,
associated with the next cardiac cycle (n), is aligned with the
time 775 that occurs a period 760 before the negative-to-positive
sign change 752.
[0067] Referring now to FIG. 13, shown therein is a graphical
representation 771 of selecting the diagnostic window 792. The
starting point 794 and/or the ending point 796 of the diagnostic
window 792 can be selected based on the sign change(s) of the
slope. For example, the diagnostic window can be selected using the
identified minima 762, 766 and maxima 764, 768 based on the sign
change(s) in the slope of the pressure waveform. In some
embodiments, the starting point 794 of the diagnostic window 792
can be offset from the peak pressure measurement, and the ending
point 796 can be offset from the minimum pressure measurements. In
some embodiments, the starting point 794 and/or the ending point
796 can selected based on different slope sign changes. For
example, the starting point 794 can be selected based on a
negative-to-positive slope sign change, and the ending point 796
can be selected based on a positive-to-negative slope sign change.
In some embodiments, the starting point 794 can be offset from the
negative-to-positive sign change, and the ending point 796 can be
offset from the positive-to-negative sign change.
[0068] In some embodiments, a computing device can identify the
maximum negative/down slope 780 that occurs after the maximum or
peak pressure value 764. The diagnostic window 792 can be selected
within the period 789 between the maximum negative/down slope value
780 and the next minimum pressure value 766. In that regard, the
computing device can select a beginning point 794 of the diagnostic
window 792 to be positioned a fixed percentage of the period 789
from the time 784. That is, the beginning point 794 of the
diagnostic window can be offset by a period 788 from the time 784
of the maximum negative/down slope value 780. A computing device
can select an ending point 796 of the diagnostic window 792 to be
positioned a fixed percentage of the period 789 from the time 786.
That is, the ending point 796 of the diagnostic window can be
offset by a period 790 from the time 786 of the next minimum
pressure value 766. One, the other, or both of the periods 788, 790
can be described as a percentage of the period 789, including
values between about 10% and about 90%, between about 12% and about
40%, between about 15% and 30%, as 15%, 20%, 25%, and/or other
suitable values both larger and smaller. For example, the period
788 can be 25% of the period 789, and the period 790 can be 15% of
the period 789.
[0069] Referring now to FIG. 14, shown therein is flow diagram of a
method 800 of evaluating a vessel of a patient. As illustrated, the
method 800 includes a number of enumerated steps, but
implementations of the method 800 may include additional steps
before, after, and in between the enumerated steps. In some
implementations, one or more of the enumerated steps may be omitted
or performed in a different order. One or more of the steps of the
method 800 may be performed by processing unit or processor, such
as the computing device 172 (FIG. 4). One or more of the steps of
the method 800 can be carried out by a user, such as a cardiologist
or other medical professional.
[0070] At step 805, the method 800 includes introducing a first
intravascular pressure-sensing instrument into a vessel of a
patient proximal of a stenosis of vessel. In some embodiments, a
catheter, guide wire, or a guide catheter with a pressure sensor
can be inserted into, e.g., a coronary artery such that at least a
portion of the instrument (e.g., the portion including the pressure
sensor) is positioned proximal of a stenosis of the vessel. At step
810, the method 800 includes introducing a second intravascular
pressure-sensing instrument into the vessel distal of the stenosis
of the vessel. In some embodiments, a catheter, guide wire, or a
guide catheter with a pressure sensor can be inserted into, e.g., a
coronary artery such that at least a portion of the instrument
(e.g., the portion including the pressure sensor) is positioned
distal of the stenosis of the vessel. In some embodiments, the
intravascular pressure-sensing instrument positioned proximally of
the stenosis is a catheter or guide catheter, and the intravascular
pressure-sensing instrument positioned distally of the stenosis is
a guide wire.
[0071] At step 815, the method 800 includes receiving, at a
computing device of an intravascular processing system, proximal
and distal pressure measurements respectively obtained by first and
second intravascular pressure-sensing instruments. The computing
device is in communication with first and second intravascular
pressure-sensing instruments. The proximal and distal pressure
measurements can be obtained during one or more cardiac cycles of
the patient. The proximal and distal pressure measurements can be
obtained without administration of a hyperemic agent to the
patient.
[0072] At step 820, the method 800 includes selecting, by the
computing device of the intravascular processing system, a
diagnostic window within the cardiac cycle of the patient. The
diagnostic window encompasses only a portion of the cardiac cycle
of the patient. In some embodiments, the selecting a diagnostic
window does not include using electrocardiogram (ECG) data to,
e.g., identify a beginning of a cardiac cycle. The diagnostic
window can be selected by identifying a change in sign of a slope
associated with at least one of the proximal pressure measurements
or the distal pressure measurements. In that regard, the method 800
can include calculating the slope over multiple time periods. In
some embodiments, a single time period encompasses only a portion
of the cardiac cycle. In some embodiments, time periods associated
with a single cardiac cycle have the same duration. In some
embodiments, a computing device or processing unit calculates the
slope over time periods of multiple cardiac cycles. The time
periods associated with a first cardiac cycles can have different
duration than the time periods associated with the second cardiac
cycle. In some embodiments, a duration of the time periods is based
on a duration of time periods in one or more previous cardiac
cycles. In some embodiments, a duration of a time period is based
on an average of earlier time period durations. In some
embodiments, consecutive time periods at least partially overlap in
time. In some embodiments, a starting point of consecutive time
periods are offset based on an acquisition rate of the at least one
pressure-sensing instrument.
[0073] The method 800 can include identifying a sign change of the
slope based on the slope calculated over the plurality of time
periods. That is, slopes respectively associated with the plurality
of segments can change polarity or sign from positive to negative
or from negative to positive. The method 800 can include
determining, based on the sign change of the slope, a minimum
pressure measurement, a peak pressure measurement, a beginning of
the cardiac cycle, an ending of the cardiac cycle, a beginning of
systole, an ending of diastole, a starting point of the diagnostic
window, and/or an ending point of the diagnostic window.
[0074] In some embodiments, the diagnostic window can be selected
based on the time during the cardiac cycle at which the sign of the
slopes changes. A computing device or processing unit can determine
a starting point of the diagnostic window based on the sign change
of the slope. The starting point of the diagnostic window can be
offset from the sign change of the slope. In some embodiments, a
peak pressure measurement can be determined based on the sign
change of the slope. The peak pressure measurement can be offset
from the sign change of the slope. A computing device or processing
unit can determine a starting point of the diagnostic window based
on the peak pressure measurement. The starting point of the
diagnostic window can be offset from the peak pressure measurement.
In some embodiments, the method 800 further determining a maximum
negative slope occurring after the peak pressure measurement. For
example, the maximum negative slope point can occur between an
identified peak pressure measurement (cardiac cycle n-1) and a next
identified minimum pressure measurement (cardiac cycle n). A
computing device or processing unit can determine a starting point
of the diagnostic window based on the maximum negative slope. The
starting point of the diagnostic window can be offset from the
maximum negative slope.
[0075] In some embodiments, the method 800 further includes
determining a second or further sign change of the slope. A
computing device or processing unit can determine a minimum
pressure measurement based on the further sign change of the slope.
The minimum pressure measurement can be offset from the further
sign change of the slope. A computing device or processing unit can
determine an ending point of the diagnostic window based on the
minimum pressure measurement. The ending point of the diagnostic
window can be offset from the minimum pressure measurement.
[0076] At step 825, the method 800 includes identifying, by the
computing device of the intravascular processing system, a
plurality of the distal pressure measurements obtained during the
diagnostic window from the received distal pressure measurements.
The plurality of distal pressure measurements are selected based on
the selected diagnostic window and are a subset of the received
distal pressure measurements. Step 825 similarly includes
identifying, by the computing device of the intravascular
processing system, a plurality of the proximal pressure
measurements obtained during the diagnostic window from the
received proximal pressure measurements. The plurality of proximal
pressure measurements are selected based on the selected diagnostic
window and are a subset of the received proximal pressure
measurements. An example of identifying a plurality of the pressure
measurements obtained during the diagnostic window is described in
U.S. application Ser. No. 13/460,296, titled "Devices, Systems, and
Methods for Assessing a Vessel," and filed Apr. 30, 2012, the
entirety of which is incorporated by reference herein.
[0077] At step 830, the method 800 includes calculating, by
computing device, a pressure ratio between an average of the
plurality of distal pressure measurements obtained during the
diagnostic window and an average of the plurality of proximal
pressure measurements obtained during the diagnostic window. An
example of calculating the pressure ratio is described in U.S.
application Ser. No. 13/460,296, titled "Devices, Systems, and
Methods for Assessing a Vessel," and filed Apr. 30, 2012, the
entirety of which is incorporated by reference herein.
[0078] At step 835, the method 800 includes outputting the
calculated pressure ratio to display device in communication with
computing device. In some embodiments, the proximal and distal
pressure measurements are aligned (with respect to time) before the
pressure ratio is calculated, as described, for example, in U.S.
application Ser. No. 14/157,404, titled "Devices, Systems, and
Methods for Assessing a Vessel," and filed Jan. 16, 2014; and/or
U.S. application Ser. No. 13/460,296, titled "Devices, Systems, and
Methods for Assessing a Vessel," and filed Apr. 30, 2012, the
entireties of which is incorporated by reference herein. For
example, alignment can be performed when the user selects a
normalization option provided by the intravascular system. Once the
normalization is ordered, the amount of misalignment is calculated
by cross-correlating the proximal and distal pressure measurements
pressure for every heart cycle until the fifth cycle. To complete
the normalization, the pressure measurements, for each heart cycle,
can be shifted by an average of the five cycles.
[0079] At step 840, the method 800 includes identifying a treatment
option based on the calculated pressure ratio. For example, the
treatment option can be no treatment, drug therapy, a percutaneous
coronary intervention (PCI), such as angioplasty and/or stenting, a
coronary artery bypass grafting (CABG) procedure, and/or other
suitable clinical interventions including combinations of the
foregoing options. At step 845, the method 800 includes performing
the identified treatment option.
[0080] Persons skilled in the art will also recognize that the
apparatus, systems, and methods described above can be modified in
various ways. Accordingly, persons of ordinary skill in the art
will appreciate that the embodiments encompassed by the present
disclosure are not limited to the particular exemplary embodiments
described above. In that regard, although illustrative embodiments
have been shown and described, a wide range of modification,
change, and substitution is contemplated in the foregoing
disclosure. It is understood that such variations may be made to
the foregoing without departing from the scope of the present
disclosure. Accordingly, it is appropriate that the appended claims
be construed broadly and in a manner consistent with the present
disclosure.
* * * * *